Cell Structure and Organisation Flashcards
How is the nucleus structured?
Surrounded by double membrane (nuclear envelope).
Has nuclear pores to allow movement of mRNA and nucleotides out.
Contains nucleoplasm.
Nucleolus- rRNA is produced.
What can be found in the nucleoplasm ?
Chromatin- loosely coiled chromosomes of DNA + histone protein.
What is formed by the outer nuclear membrane?
Endoplasmic reticulum
What is the function of mitochondria (s. Mitochondrion)?
Aerobic respiration occurs to produce ATP.
Where are many mitochondria found?
Muscle tissue for contraction and liver tissue which is metabolically active
Structure of a mitochondrion-
Cristae- double membrane sac with highly folded inner membrane, increasing surface are.
Matrix-liquid containing enzymes for aerobic respiration
Ribosomes
Circular DNA- self replicating
What are the two forms of endoplasmic reticulum and what are their functions?
Smooth- synthesises lipids
Rough- ribosomes are attached that synthesise proteins
What is the structure of ER?
Consists of flattened sacs called cisternae which extend into cytoplasm and can link with the golgi body
What is the function of the nucleus?
It contains the cell’s DNA which provides the code for protein synthesis. mRNA leaves via the nuclear pores carrying the code.
How are ribosomes structured?
Very small not membrane-bound
Composed of 2 sub-units, large and small.
Come together around mRNA strand which fits into a groove
What are ribosomes made of?
Protein and rRNA
Where can ribosomes be found?
On RER or free in cytoplasm (called polysomes)
What is ribosomes’ function?
Protein synthesis
What is the golgi body (apparatus)?
A crescent shaped stack of flattened membrane-bound sacs called cisternae.
What are the functions of the golgi body?
Chemically modifies proteins to form glycoproteins.
Stores and transports glycoproteins and lipids
What is the first part of the golgi body process for glycoproteins?
Vesticles containing proteins formed by RER fuse at one end of golgi sacs (forming face)
What are the second and third parts of the golgi body process for glycoproteins?
- The protein is modified inside the cisternae.
3. Modified protein is budded off in a vesticle at other end of cisternae (maturing face)
What is the final part of the golgi body process for glycoproteins?
The vesticle containing modified protein travels to cell’s outer plasma membrane where the protein is released via exocytosis
What is the structure of plasma membrane?
Formed of a phospholipid bilayer with intrinsic and extrinsic proteins and other molecules embedded into it
What are the 3 properties/functions of plasma membranes?
- Selectively permeable so controls substances going in and out.
- Maintains concentration difference of molecules on either side of the membrane.
- allows cell identification and adhesion
Which two organelles can only be found in animal cells?
Lysosomes and centrioles
Which 3 organelles can only be found in plants?
Chloroplasts, Vacuole with tonoplasts and Cellulose Cell Wall
What are lysosomes?
Small vacuoles surrounded by a membrane formed by pieces of golgi apparatus pinched off the end.
What is the function of lysosomes?
Break down worn out organelles and digest material taken in via phagocytosis
What type of enzymes are within a lysosome?
Protein digesting
What is the action of the lysosomes?
Material taken into cell by endocytosis and trapped in vacuole.
Lysosomes fuse with vacuole membrane and release digestive enzymes, breaking down the material.